The present invention relates to an ink jet head, a method for producing an ink jet head, and an ink jet type recording apparatus.
In the prior art, ink jet type recording apparatuses for recording information by utilizing a piezoelectric effect of a piezoelectric element have been used as printers, word processors, facsimiles, and the like. Typically, an ink jet head for use in a recording apparatus of this type includes a plurality of pressure chambers containing ink, a plurality of nozzles communicated to the pressure chambers, respectively, and an actuator for applying a pressure on the ink in the pressure chamber so as to discharge ink through the nozzle. Some of such actuators are made of a large number of thin films layered together, as illustrated in FIG. 26, for example.
In an ink jet head as described above, a head body 101 is provided with a plurality of pressure chamber depressions 102 arranged in the direction indicated by X1 in the figure. A vibration plate 104 is provided on the head body 101 so as to cover the plurality of pressure chamber depressions 102, so that the vibration plate 104 and the pressure chamber depression 102 of the head body 101 define a pressure chamber 103, A piezoelectric element 105 made of PZT is provided on the vibration plate 104 so as to correspond to each pressure chamber 103, and a separate electrode 106 made of Pt (platinum) is provided on the piezoelectric element 105. Note that the vibration plate 104 is made of Cr (chromium) and functions also as a common electrode of the piezoelectric element 105. The vibration plate 104, the piezoelectric element 105 and the separate electrode 106 together form an actuator. When discharging ink, a voltage is applied between the separate electrode 106 and the vibration plate 104 as a common electrode so as to expand/contract the piezoelectric element 105. Thus, the vibration plate 104 fixed to the piezoelectric element 105 undergoes flexural deformation so as to pressurize the ink in the pressure chamber 103, thereby discharging the ink through a nozzle (not shown).
In recent years, the thickness of the piezoelectric element 105 has been reduced as the ink jet heads have been downsized. However, as the thickness of the piezoelectric element 105 is reduced, the voltage endurance is reduced. Thus, the reduction in the thickness increases the possibility of dielectric breakdown occurring upon application of a voltage. Dielectric breakdown occurring in the piezoelectric element 105 not only reduces the ink discharging performance, but may also leads to leakage of the ink in the pressure chamber 103 to the outside if the degree of dielectric breakdown is high. In view of this, a technique for preventing dielectric breakdown of the piezoelectric element 105 has been longed for in order to improve the reliability of the ink jet head.
As one of such techniques, there is a technique of improving the voltage endurance of the piezoelectric element itself by modifying the crystal structure of a piezoelectric material, as disclosed in Japanese Laid-Open Patent Publication No. 10-217458.
However, during the formation of the piezoelectric element in the process of producing an ink jet head, a defective portion 107 may occur in the piezoelectric element 105 as illustrated in FIG. 27 due to impurities in the production apparatus being introduced into the piezoelectric element or due to the influence of the thermal stress of the piezoelectric element. Therefore, even when the voltage endurance of the material of the piezoelectric element 105 itself is high, the presence of such a defective portion 107 makes the piezoelectric element 105 structurally liable to dielectric breakdown. Specifically, in a case where the defective portion 107 is conductive (e.g., where conductive impurities are introduced), the portion of the piezoelectric element 105 corresponding to the defective portion 107 becomes a portion with a locally reduced thickness, thereby significantly reducing the voltage endurance. Moreover, even in a case where the defective portion 107 is insulative, the piezoelectric element 105 has a non-uniform thickness at the defective portion 107, whereby an electric field localization is likely to occur upon application of a voltage. Therefore, dielectric breakdown is likely to occur in this portion. Particularly, as the thickness of the piezoelectric element is more reduced, the proportion of the defective portion with respect to the piezoelectric element increases. Therefore, the possibility of dielectric breakdown in the piezoelectric element becomes even higher as the thickness of the piezoelectric element is reduced.
Thus, a new technique of preventing the dielectric breakdown of the piezoelectric element in view of the defect which may occur during the formation of the piezoelectric element has been longed for. Moreover, in order to prevent the dielectric breakdown of the piezoelectric element, a new technique of detecting a defect in the piezoelectric element and a new technique of improving the voltage endurance of the piezoelectric element have been longed for.
The present invention has been made in view of the above, and has an object to provide an ink jet head, an ink jet type recording apparatus and a method for producing the same in which the voltage endurance of the piezoelectric element is not reduced even when a defect is included therein.
Moreover, another object is to provide a method for producing an ink jet head in which a defect in the piezoelectric element is detected by a simple method so as to improve the voltage endurance of the piezoelectric element based on the detection. Moreover, another object is to provide an ink jet head and an ink jet type recording apparatus in which the piezoelectric element has a high voltage endurance.
In one embodiment of the present invention, a portion of an upper electrode or a lower electrode corresponding to a defective portion of a piezoelectric element is removed by dielectric breakdown so that an applied voltage is locally absent in the defective portion of the piezoelectric element.
In another embodiment of the present invention, a voltage is applied between an upper electrode and a lower electrode, and a defective portion is detected based on the temperature distribution of the upper electrode or the lower electrode.
In another embodiment of the present invention, a voltage is applied between an upper electrode and a lower electrode to cause minute dielectric breakdown, and a dielectric breakdown portion thereof is detected so as to detect a defective portion.
Specifically, an ink jet head production method according to the present invention is a method for producing an ink jet head for discharging ink by a piezoelectric effect of a piezoelectric element, the method including: a step of, after the piezoelectric element and an upper electrode and a lower electrode of the piezoelectric element are formed, removing, through dielectric breakdown, a portion of the upper electrode or the lower electrode corresponding to a defective portion of the piezoelectric element.
Thus, a portion of the upper electrode or the lower electrode corresponding to the defective portion of the piezoelectric element is removed, whereby at least one of an upper portion or a lower portion overlying/underlying the defective portion of the piezoelectric element becomes an electrode discontinuity portion where the electrode is locally absent. Accordingly, no voltage is applied through the defective portion of the piezoelectric element. Therefore, even if a defect is included in the piezoelectric element, no dielectric breakdown occurs, whereby the voltage endurance of the piezoelectric element does not deteriorate.
The thickness of the piezoelectric element may be 0.5 xcexcm to 5 xcexcm.
Thus, the voltage endurance does not deteriorate even though the piezoelectric element is a thin film, whereby the effect of improving the voltage endurance becomes particularly significant.
Another ink jet head production method according to the present invention is an a method for producing an ink jet head, the ink jet head including: a head body which is provided with a plurality of pressure chambers containing ink and a plurality of nozzles communicated to the pressure chambers, respectively; and a plurality of actuators each having a piezoelectric element and a vibration plate for deforming the vibration plate to apply a pressure on the ink in each of the pressure chambers by a piezoelectric effect of the piezoelectric element so as to discharge the ink through each of the nozzles, the method including: a step of depositing a lower electrode on a first base material; a step of depositing a piezoelectric element on the lower electrode; an upper electrode deposition step of depositing an upper electrode on the piezoelectric element; and a dielectric breakdown step of applying a predetermined voltage between the upper electrode and the lower electrode so as to remove, through dielectric breakdown, a portion of the upper electrode corresponding to a defective portion of the piezoelectric element.
Thus, when a defective portion occurs during the formation of the piezoelectric element, the predetermined voltage applied between the upper electrode and the lower electrode causes minute dielectric breakdown of such a degree that the other portions of the piezoelectric element or the upper electrode are not broken, thereby heating the defective portion or a portion of the upper electrode corresponding to the defective portion, with the heat melting and vaporizing a portion of the upper electrode. Therefore, a portion of the upper electrode corresponding to the defective portion of the piezoelectric element is removed easily and smoothly.
The application of the predetermined voltage in the dielectric breakdown step may be performed after patterning the upper electrode.
Thus, as compared to the case where the predetermined voltage is applied before patterning (separating) the electrode, the area of the electrodes at the time of the voltage application is reduced, whereby the amount of charge stored between the electrodes is reduced. Therefore, the current flowing through the defective portion of the piezoelectric element is reduced, whereby the dielectric breakdown can be easily suppressed to a minute degree. Thus, the minute dielectric breakdown for detecting a defective portion can be easily controlled.
The method may include, after the dielectric breakdown step, a step of embedding an insulator in a removed portion of the upper electrode.
Thus, since the portion where dielectric breakdown has occurred is filled up with an insulator, the application of a normal voltage through the defective portion of the piezoelectric element is reliably prevented. Moreover, ink is prevented from entering the portion from a pressure chamber.
Alternatively, the method may include, after the dielectric breakdown step, a step of covering a removed portion of the upper electrode by an insulator.
Thus, since the portion where dielectric breakdown has occurred is covered by an insulator, the application of a normal voltage through the defective portion of the piezoelectric element is reliably prevented. Moreover, ink is prevented from entering the portion from a pressure chamber.
The method may include, after the dielectric breakdown step: an insulative layer formation step of depositing an insulative layer on the upper electrode; a vibration plate deposition step of depositing a vibration plate on the insulative layer; a step of attaching a second base material, which has been provided with a plurality of pressure chamber depressions and nozzles, to the vibration plate so that the pressure chamber depressions are covered by the vibration plate, whereby a plurality of pressure chambers are defined by the pressure chamber depressions and the vibration plate; a step of removing the first base material; and a step of patterning the lower electrode and the piezoelectric element so as to correspond to the respective pressure chambers.
Thus, the portion where dielectric breakdown has occurred is filled up with an insulator or covered by an insulative layer, as described above, whereby the portion becomes a no-voltage-application portion where the applied normal voltage is locally absent. Therefore, since no voltage is applied through the defective portion, the voltage endurance of the piezoelectric element is maintained. Moreover, ink is prevented from entering the portion from a pressure chamber.
The method may include a step of depositing an insulative vibration plate on the upper electrode, instead of the insulative layer formation step and the vibration plate deposition step.
Thus, an ink jet head in which the vibration plate functions also as an insulative layer is obtained.
The method may include, after the dielectric breakdown step: an insulative layer formation step of depositing an insulative layer on the upper electrode; a vibration plate deposition step of depositing a vibration plate on the insulative layer; a step of providing a plurality of pressure chambers and nozzles in the first base material; and a step of patterning the vibration plate so as to correspond to the respective pressure chambers.
Thus, the portion where dielectric breakdown has occurred is filled up with an insulator or covered by an insulative layer, as described above, whereby the portion becomes a no-voltage-application portion where the applied normal voltage is locally absent. Therefore, since no voltage is applied through the defective portion, the voltage endurance of the piezoelectric element is improved. Moreover, ink is prevented from entering the portion from a pressure chamber.
The method may include a step of depositing an insulative vibration plate on the upper electrode, instead of the insulative layer formation step and the vibration plate deposition step.
Thus, an ink jet head in which the vibration plate function also as an insulative layer is obtained.
When the voltage value of the voltage applied in the dielectric breakdown step is set to be larger than the normal voltage, such a degree of dielectric breakdown that would occur when applying the normal voltage will always occur in the dielectric breakdown step. Conversely, if dielectric breakdown does not occur when applying a voltage larger than the normal voltage, dielectric breakdown will not occur when applying the normal voltage. In view of this, the voltage value of the applied voltage is preferably large. However, when the duration for which the application voltage is applied is excessive, the dielectric breakdown may spread out. Therefore, the duration for which the predetermined voltage is applied is preferably short in order to cause dielectric breakdown only in portions where it is required.
In view of this, the predetermined voltage used in the dielectric breakdown step may be a pulse voltage having a larger voltage value and a shorter application duration than a normal pulse voltage, which is applied for deforming the vibration plate for discharging ink.
Thus, the voltage endurance of the piezoelectric element is highly ensured. Moreover, only a portion of the electrode layer corresponding to the defective portion of the piezoelectric layer is removed smoothly.
The thickness of the upper electrode may be less than or equal to the thickness of the lower electrode.
Thus, it is possible to easily remove only the upper electrode without removing the lower electrode for the portion corresponding to the defective portion of the piezoelectric element, thereby facilitating the subsequent repairing of the removed portion.
Another ink jet head production method according to the present invention is a method for producing an ink jet head, the ink jet head including: a head body which is provided with a plurality of pressure chambers containing ink and a plurality of nozzles communicated to the pressure chambers, respectively; and a plurality of actuators each having a piezoelectric element and a vibration plate for deforming the vibration plate to apply a pressure on the ink in each of the pressure chambers by a piezoelectric effect of the piezoelectric element so as to discharge the ink through each of the nozzles, the method including: a step of depositing a lower electrode on a first base material; a step of depositing a piezoelectric element on the lower electrode; a step of depositing a conductive vibration plate on the piezoelectric element; a dielectric breakdown step of applying a predetermined voltage between the conductive vibration plate and the lower electrode so as to remove, through dielectric breakdown, a portion of the conductive vibration plate corresponding to a defective portion of the piezoelectric element; a step of depositing an insulative layer on the conductive vibration plate; a step of attaching a second base material, which has been provided with a plurality of pressure chamber depressions and nozzles, to the insulative layer so that the pressure chamber depressions are covered by the insulative layer, whereby a plurality of pressure chambers are defined by the pressure chamber depressions and the insulative layer; a step of removing the first base material; and a step of patterning the lower electrode and the piezoelectric element so as to correspond to the respective pressure chambers.
Thus, since the vibration plate is conductive, the vibration plate functions also as the upper electrode. Therefore, it is no longer necessary to separately provide the vibration plate and the upper electrode. Moreover, the portion where dielectric breakdown has occurred is filled up with an insulator or covered by an insulative layer, as described above, whereby the portion becomes a no-voltage-application portion where the applied normal voltage is locally absent, thus improving the voltage endurance of the piezoelectric element.
The application of the predetermined voltage in the dielectric breakdown step may be performed after patterning the conductive vibration plate.
Thus, as compared to the case where the predetermined voltage is applied before patterning (separating) the electrode, the area of the electrodes at the time of the voltage application is reduced, whereby the amount of charge stored between the electrodes is reduced. Therefore, the current flowing through the defective portion of the piezoelectric element is reduced, whereby the dielectric breakdown can be easily suppressed to a minute degree. Thus, the minute dielectric breakdown for detecting a defective portion can be easily controlled.
Another ink jet head production method according to the present invention is a method for producing an ink jet head, the ink jet head including: a head body which is provided with a plurality of pressure chambers containing ink and a plurality of nozzles communicated to the pressure chambers, respectively; and a plurality of actuators each having a piezoelectric element and a vibration plate for deforming the vibration plate to apply a pressure on the ink in each of the pressure chambers by a piezoelectric effect of the piezoelectric element so as to discharge the ink through each of the nozzles, the method including: a step of depositing a lower electrode on a first base material; a step of depositing a piezoelectric element on the lower electrode; a step of depositing a conductive vibration plate on the piezoelectric element; a dielectric breakdown step of applying a predetermined voltage between the conductive vibration plate and the lower electrode so as to remove, through dielectric breakdown, a portion of the conductive vibration plate corresponding to a defective portion of the piezoelectric element; a step of depositing an insulative layer on the conductive vibration plate; a step of providing a plurality of pressure chambers and nozzles in the first base material; and a step of patterning the conductive vibration plate and the insulative layer so as to correspond to the respective pressure chambers.
Thus, since the vibration plate is conductive, the vibration plate functions also as the upper electrode, as described above. Therefore, it is no longer necessary to separately provide the vibration plate and the upper electrode. Moreover, the portion where dielectric breakdown has occurred is filled up with an insulator or covered by an insulative layer, as described above, whereby the portion becomes a no-voltage-application portion where the applied normal voltage is locally absent, thus improving the voltage endurance of the piezoelectric element.
The application of the predetermined voltage in the dielectric breakdown step may be performed after patterning the conductive vibration plate.
Thus, as compared to the case where the predetermined voltage is applied before patterning (separating) the electrode, the area of the electrodes at the time of the voltage application is reduced, whereby the amount of charge stored between the electrodes is reduced. Therefore, the current flowing through the defective portion of the piezoelectric element is reduced, whereby the dielectric breakdown can be easily suppressed to a minute degree. Thus, the minute dielectric breakdown for detecting a defective portion can be easily controlled.
An ink jet head according to the present invention is an ink jet head for discharging ink by a piezoelectric effect of a piezoelectric element, wherein: a first electrode and a second electrode for applying a voltage through the piezoelectric element are provided respectively on opposite sides of the piezoelectric element; and a discontinuity portion is formed through dielectric breakdown in at least one of the first and second electrodes.
Thus, no voltage is applied through the defective portion of the piezoelectric element, whereby an ink jet head having a piezoelectric element with a desirable voltage endurance is obtained.
An insulator may be embedded in the discontinuity portion of the first or second electrode.
Thus, the discontinuity portion is filled up with an insulator, whereby the application of a normal voltage through the defective portion of the piezoelectric element is reliably prevented.
The discontinuity portion of the first or second electrode may be covered by an insulator.
Thus, the discontinuity portion is covered by an insulator, whereby the application of a normal voltage through the defective portion of the piezoelectric element is reliably prevented.
The thickness of the piezoelectric element may be 0.5 xcexcm to 5 xcexcm.
Thus, the voltage endurance does not deteriorate even though the piezoelectric element is a thin film, whereby the effect of improving the voltage endurance becomes particularly significant.
Another ink jet head according to the present invention is an ink jet head ink jet head for discharging ink by a piezoelectric effect of a piezoelectric element, wherein: a first electrode and a second electrode for applying a voltage through the piezoelectric element are provided respectively on opposite sides of the piezoelectric element; a thickness of the first electrode is less than or equal to a thickness of the second electrode; and a discontinuity portion is formed through dielectric breakdown in the first electrode.
Thus, no voltage is applied through the defective portion of the piezoelectric element, whereby an ink jet head having a piezoelectric element with a desirable voltage endurance is obtained.
The thickness of the piezoelectric element may be 0.5 xcexcm to 5 xcexcm.
Thus, the voltage endurance does not deteriorate even though the piezoelectric element is a thin film, whereby the effect of improving the voltage endurance becomes particularly significant.
Another ink jet head production method according to the present invention is a method for producing an ink jet head for discharging ink by a piezoelectric effect of a piezoelectric element, the method including: a step of, after the piezoelectric element and an upper electrode and a lower electrode of the piezoelectric element are formed, detecting a temperature distribution of at least one of the upper electrode and the lower electrode while applying a predetermined voltage between the upper electrode and the lower electrode so as to detect a defective portion of the piezoelectric element based on the temperature distribution.
Thus, when a voltage is applied between the upper electrode and the lower electrode, if a defect is included in the piezoelectric element, minute dielectric breakdown occurs in the defective portion, thereby heating the piezoelectric element. Therefore, it is possible to find the defective portion of the piezoelectric element by detecting the portion whose temperature takes an extreme value (the maximum value or the minimum value).
The temperature of the upper electrode or the lower electrode may be measured by temperature detection means for periodically detecting a temperature; and a plurality of pulse voltages may be applied, as the predetermined voltage, at a cycle less than or equal to the detection cycle of the temperature detection means.
Thus, when a plurality of pulse voltages are applied as the predetermined voltage, unlike the case where a constant voltage is applied for a long time, excessive heating of the upper electrode or the lower electrode is prevented. Moreover, when the cycle of the plurality of pulse voltages is excessively long, the temperature distribution created by the voltage application is leveled out, thereby making the detection of the defective portion difficult. However, according to the above, the cycle of the pulse voltages is less than or equal to the detection cycle of the temperature detection means, whereby it is easy to detect the defective portion.
Each of the pulse voltages may be a pulse voltage having a larger voltage value and a shorter application duration than a normal pulse voltage, which is applied for discharging ink.
Thus, when the voltage value of the pulse voltages is set to be larger than voltage value of the normal pulse voltage, such a degree of dielectric breakdown that would occur when applying the normal pulse voltage will always occur when applying the pulse voltages. Conversely, if dielectric breakdown does not occur by the application of the pulse voltages, dielectric breakdown will not occur when applying the normal pulse voltage. Therefore, the voltage endurance of the piezoelectric element is highly ensured. Moreover, since the duration for which each pulse voltage is applied is shorter than the duration for which the normal pulse voltage is applied, excessive heating of the upper electrode or the lower electrode is prevented, and breakdown of an electrode due to heating is unlikely to occur.
The temperature of the upper electrode or the lower electrode may be detected by temperature detection means for detecting a temperature by elements each having a predetermined size; and the method may include a step of, after an extreme value element for which the detected temperature is maximum or minimum is identified among a plurality of elements, identifying a peak temperature portion within the extreme value element based on a temperature distribution among a plurality of adjacent elements which are adjacent to the extreme value element.
Thus, first, the temperature distribution of the upper electrode or the lower electrode is detected by the temperature detection means having a predetermined resolution in the unit of elements according to the resolution. Then, the temperature of each of the plurality of elements is detected, and the element for which the detected temperature is higher than that of any of the adjacent elements or the element for which the detected temperature is lower than that of any of the adjacent elements is identified as the extreme value element. Then, the temperature distribution within the extreme value element is estimated by interpolation, or the like, based on the temperature distribution among the plurality of adjacent elements which are adjacent to the extreme value element, and a portion where the temperature takes the maximum value or the minimum value within the extreme value element (the peak temperature portion) is identified. Therefore, it is possible to detect the temperature distribution at a resolution equal to or greater than the inherent resolution of the temperature detection means, and to detect a very small defective portion.
The method may include a step of, after a defective portion of the piezoelectric element is detected, removing a portion of the upper electrode or the lower electrode corresponding to the defective portion or a portion of the upper electrode or the lower electrode corresponding to a surrounding portion around the defective portion.
Thus, a portion of the upper electrode or the lower electrode corresponding to the defective portion becomes a discontinuity portion where the electrode is locally absent or an isolated portion which is isolated from the other electrode portions, whereby no voltage is applied through the defective portion of the piezoelectric element during the ink discharging operation. Therefore, dielectric breakdown is unlikely to occur, thereby improving the voltage endurance of the piezoelectric element.
The method may include a step of embedding an insulator in a removed portion of the upper electrode or the lower electrode.
Thus, the portion where dielectric breakdown has occurred is filled up with an insulator, whereby the application of a voltage through the portion is reliably prevented.
The method may include a step of covering a removed portion of the upper electrode or the lower electrode by an insulator.
Thus, the portion where dielectric breakdown has occurred is covered by an insulator, whereby the application of a voltage through the portion is reliably prevented.
The application of the predetermined voltage may be performed after patterning at least one of the upper electrode and the lower electrode.
Thus, as compared to the case where the predetermined voltage is applied before patterning (separating) the electrode, the area of the electrodes at the time of the voltage application is reduced, whereby the amount of charge stored between the electrodes is reduced. Therefore, the current flowing through the defective portion of the piezoelectric element is reduced, whereby the dielectric breakdown can be easily suppressed to a minute degree. Thus, the minute dielectric breakdown for detecting a defective portion can be easily controlled.
Another ink jet head production method according to the present invention is a method for producing an ink jet head for discharging ink by a piezoelectric effect of a piezoelectric element, the method including: a step of, after the piezoelectric element and an upper electrode and a lower electrode of the piezoelectric element are formed, applying a predetermined voltage between the upper electrode and the lower electrode and detecting a dielectric breakdown portion in the upper electrode or the lower electrode which has been created due to the voltage application so as to detect a defective portion of the piezoelectric element.
Thus, when a minute voltage is applied between the upper electrode and the lower electrode, if a defect has occurred in the piezoelectric element, minute dielectric breakdown occurs in the portion. As a result, a portion of the upper electrode or the lower electrode corresponding to the defective portion of the piezoelectric element is scattered away, thereby forming a discontinuity portion in the upper electrode or the lower electrode. Then, the defect of the piezoelectric element is detected by detecting the discontinuity portion with a microscope, or the like.
The method may include a step of, after a defective portion of the piezoelectric element is detected, removing a portion of the upper electrode or the lower electrode corresponding to the defective portion or a portion of the upper electrode or the lower electrode corresponding to a surrounding portion around the defective portion.
Thus, a portion of the upper electrode or the lower electrode corresponding to the defective portion becomes a discontinuity portion where the electrode is locally absent or an isolated portion which is isolated from the other electrode portions, whereby no voltage is applied through the defective portion of the piezoelectric element during the ink discharging operation. Therefore, dielectric breakdown is unlikely to occur, thereby improving the voltage endurance of the piezoelectric element.
The method may include a step of embedding an insulator in a removed portion of the upper electrode or the lower electrode.
Thus, the portion where dielectric breakdown has occurred is filled up with an insulator, whereby the application of a voltage through the portion is reliably prevented.
The method may include a step of covering a removed portion of the upper electrode or the lower electrode by an insulator.
Thus, the portion where dielectric breakdown has occurred is covered by an insulator, whereby the application of a voltage through the portion is reliably prevented.
The application of the predetermined voltage may be performed after patterning at least one of the upper electrode and the lower electrode.
Thus, as compared to the case where the predetermined voltage is applied before patterning (separating) the electrode, the area of the electrodes at the time of the voltage application is reduced, whereby the amount of charge stored between the electrodes is reduced. Therefore, the current flowing through the defective portion of the piezoelectric element is reduced, whereby the dielectric breakdown can be easily suppressed to a minute degree. Thus, the minute dielectric breakdown for detecting a defective portion can be easily controlled.
Another ink jet head according to the present invention is an ink jet head ink jet head for discharging ink by a piezoelectric effect of a piezoelectric element, wherein: a first electrode and a second electrode for applying a voltage through the piezoelectric element are provided respectively on opposite sides of the piezoelectric element; and a discontinuity portion is formed in at least one of the first and second electrodes, the discontinuity portion being provided by removing a portion corresponding to a defective portion of the piezoelectric element or a portion corresponding to a surrounding portion around the defective portion.
Thus, a portion of an electrode on one side or both sides of the piezoelectric element corresponding to the defective portion is removed, whereby an ink jet head having a piezoelectric element with a desirable voltage endurance is obtained.
An insulator may be embedded in a discontinuity portion of the first or second electrode.
Thus, the application of a voltage through the it defective portion of the piezoelectric element is reliably prevented, thereby improving the voltage endurance of the piezoelectric element.
A discontinuity portion of the first or second electrode may covered by an insulator.
Thus, the application of a voltage through the defective portion of the piezoelectric element is reliably prevented, thereby improving the voltage endurance of the piezoelectric element.
An ink jet type recording apparatus according to the present invention includes any of the ink jet head described above.
Thus, a reliable ink jet type recording apparatus having a piezoelectric element with a desirable voltage endurance is obtained.
As described above, according to the present invention, minute dielectric breakdown is caused in a defective portion of a piezoelectric element during the head production process so as to remove beforehand a portion of the upper electrode or the lower electrode overlying/underlying the piezoelectric element corresponding to the defective portion, whereby the defective portion of the piezoelectric element can be a no-voltage-application portion where the applied voltage is locally absent. Therefore, even if a defective portion is included in the piezoelectric element, no voltage is applied through the defective portion during the application of a normal voltage, whereby it is possible to prevent dielectric breakdown from occurring. Therefore, even when the thickness of the piezoelectric element is reduced, the voltage endurance thereof can be desirably maintained.
By filling up the discontinuity portion of the upper electrode or the lower electrode with an insulator, or by covering the discontinuity portion by an insulator, the voltage endurance of the piezoelectric element can be further improved. Moreover, ink is prevented from entering the defective portion.
Moreover, according to the present invention, the defective portion of the piezoelectric element can be easily detected. Therefore, it is possible to increase the voltage endurance of the piezoelectric element by subsequently removing or repairing the defective portion.
With an ink jet head and an ink jet type recording apparatus according to the present invention, no voltage is applied through a defective portion of a piezoelectric element, whereby no dielectric breakdown occurs. Therefore, an ink jet head and an ink jet type recording apparatus having a piezoelectric element with a desirable voltage endurance can be obtained.